Pressure sensitive adhesive (PSA) coated films (e.g., sun control window films and anti-graffiti films) that are applied to window glass or other substrates are often applied with the aid of an application fluid typically comprising about 0.1 to about 1 percent weight soap in water. The application fluid aids in the positioning of the film on the substrate by interfering with the bond of the PSA with the substrate thereby allowing the film to easily slide across the substrate. The application fluid is sprayed onto the glass and/or the pressure sensitive adhesive in a fine mist so that relatively uniform coverage of the pressure sensitive adhesive and the substrate is obtained. The pressure sensitive adhesive coated film is then brought into contact with the substrate. The application fluid trapped between the PSA-coated film and the substrate is then removed by squeegeeing the application fluid to an outer edge of the film. Window films of the type applied using this technique typically have a thickness ranging from about 40-250 xcexcm and comprise one or more layers of polymer film (e.g., PET film) and may further include semi-transparent metal coatings (e.g., vapor deposited aluminum).
Due to the relatively thin nature of these window films, the films are usually sized larger in one or more dimensions than the size of the substrate to which they are to be applied. Once the application fluid is removed from between the film and the substrate, the film is trimmed to the desired size using a sharp instrument, for example, a razor blade or utility knife.
Although the above described technique has gained acceptance for the application of relatively thin PSA-coated films, films having a thickness greater than about 250 xcexcm are generally not suitable for application using this technique since they cannot be easily trimmed in place. Therefore, these films are preferably precisely cut to the size of the substrate prior to application to the substrate. During application, it is desirable to substantially center the film on the substrate leaving a small (e.g., nominal 0.060 inch) gap around the entire periphery of the film between the edge of the film and the edge of the substrate (e.g., a window frame). The gap between the edge of the film and the edge of the substrate is desirable as it provides an outlet point for application fluid squeegeed from between the film and the substrate. If the application fluid is not properly removed from between the film and the substrate, the film will not properly bond to the substrate.
In view of the foregoing, a method of applying an adhesive coated film (e.g., a window film) to a substrate that allows for precise positioning and alignment of the film on the substrate is desired.
The method of adhesively bonding an adhesive coated semi-rigid film to a substrate according to the present invention comprises the steps of:
(1) providing a semi-rigid film having a first side having a surface area and an opposite second side having a surface area wherein at least a portion of the surface area of the second side is coated with a bonding layer comprising a pressure sensitive adhesive;
(2) providing a substrate having a major surface and an outer edge;
(3) providing a first alignment tool;
(4) positioning the first alignment tool such that it substantially contacts the major surface of the substrate at the outer edge thereof;
(5) providing a second alignment tool;
(6) positioning the second alignment tool such that it substantially contacts the major surface of the substrate at the outer edge; wherein the first and the second alignment tools are separated from one another at a distance;
(7) optionally, applying an application fluid to the surface of the substrate or to the bonding layer of the semi-rigid film;
(8) interposing the semi-rigid film between the first and the second alignment tools;
(9) contacting the major surface of the substrate and the bonding layer of the film with one another such that, if present, at least a portion of the application fluid is present between the semi-rigid film and the substrate;
(10) aligning the semi-rigid film by contacting a first side edge of the semi-rigid film with a major surface of a first alignment tool and contacting a second side edge of the semi-rigid film with a major surface of a second alignment tool such that the film is aligned relative to the edge of the substrate;
(11) applying pressure to at least a portion of the surface area of the first side of the semi-rigid film to effectuate adhesive bonding of the film to the major surface of the substrate and, if present, forcing at least a portion of the application fluid present between the semi-rigid film and the substrate to flow out from between the semi-rigid film and the substrate at an edge;
(12) optionally, drying the application fluid that has been forced from between the film and the substrate; and
(13) optionally, removing the alignment tools.
In a preferred embodiment, the method of the present invention further includes the step of:
positioning a third alignment tool such that it substantially contacts the major surface of the substrate at the outer edge thereof at a distance from the first alignment tool and at a distance from the second alignment tool.
In a preferred embodiment, the method further including the step of:
positioning a fourth alignment tool such that it substantially contacts the major surface of the substrate at the outer edge of the substrate and at a distance from the first alignment tool and at a distance from the second alignment tool and at a distance from the third alignment tool.
In a preferred embodiment, the substrate is glass, acrylic, or polycarbonate.
In a preferred embodiment, the substrate is a window and the window has an outer frame defining the outer edge of the substrate.
In a preferred embodiment, the first and the second alignment tools are attached to the frame of the window.
In a preferred embodiment, the first and second alignment tools are attached to the frame of the window using adhesive tape, adhesive, magnets, spring clips, or a combination thereof.
In a preferred embodiment, the first and second alignment tools each comprise:
an elongate base section adapted to be attached to the window frame; and
an elongate flange extending from the base section wherein the flange has a length and a substantially uniform thickness along the length.
In a preferred embodiment, the flange of the alignment tool has a thickness ranging from about 0.05 inches to about 0.5 inches.
In a preferred embodiment the flange has a thickness ranging from about 0.06 to about 0.120 inches.
In a preferred embodiment, the window is rectangular in shape having four substantially linear edges separated by corners and wherein the first alignment tool is positioned along one edge and wherein the second alignment tool is positioned along a second edge adjacent to the first edge.
In a preferred embodiment, the applying pressure step comprises squeegeeing the window film against the substrate.
In the preferred embodiment, the application fluid comprises water and surfactant, a soap, or combination thereof.
In a preferred embodiment, the semi-rigid film comprises:
a stack of sheets, wherein each sheet independently comprises:
(a) a film, the film having a first side having a surface area and an opposite second side having a surface area;
(b) a bonding layer having a first side having a surface area and an opposite second side having a surface area, wherein the bonding layer is bonded via its first side to the second side of the film such that at least a center of the surface area of the second side of the film is in contact with the bonding layer, wherein at least about 50 percent of the surface area of the second side of the film has the bonding layer bonded thereto;
(c) an optional release layer coated on the first side of the film;
wherein each sheet is stacked upon another sheet such that except for a bottom sheet of the stack of sheets, the bonding layer of a sheet is in contact with the protective film or release layer, if present, of a sheet below;
wherein a topmost sheet can be removed from the stack of sheets by pulling it away from the stack such that the sheet being removed from the stack as well as the sheets remaining with the stack do not delaminate.
The present invention also provides a kit for application of a semi-rigid film to a substrate comprising:
(a) a semi-rigid film having a first side having a surface area and an opposite second side having a surface area wherein at least a portion of the surface area of the second side is coated with a bonding layer comprising a pressure sensitive adhesive;
(b) a first alignment tool; and
(c) a second alignment tool.